Question

a) Explain how a sodium ion (Na+ 1) is created, its stability and why it takes on this charge. List the following values to help you answer this question: the size of the sodium ion; atomic size of the neutral atom and the Effective nuclear charge; each ionizations potential for each electron in the atom; the electron affinity and the electronegativity. Reference your source for this information.

b) Explain atomic size, ionization potential, electronegativity and the general periodic trend for each of these properties. Arrange the following atoms: O, Se, C, Si, F in order of increasing atomic radius, in order of increasing electronegativity and in order of increasing ionization energy. Explain how you developed your list and explain the similarities or differences between the lists.

Answer 1

Solution.

a)  A sodium ion is formed as a result of losing one electron by a neutral sodium atom. Electron is negatively charged, that is why a sodium ion bears a positive charge. Losing one electron, sodium becomes an ion with a vary stable noble-gas outermost electron shell.

The reference data listed below:

the size of the sodium ion - 116 pm;

atomic size of the neutral atom - 154 pm;

effective nuclear charge -1.64;

ionization potentials 495.8 kJ/mol ; 4562.4 kJ/mol; 6912 kJ/mol; 9543 kJ/mol;

electron affinity 53.2 kJ/mol;

electronegativity 0.9.

b) Atomic radius increases down a group and decreases across a period. The order of increasing atomic radius is

F<O<C<Si<Se

Ionization energy decreases down a group and increases across a period.

The order of increasing ionization energy is Si<Se<C<O<F.

The similar trends can be applied to the electronegativity.

The order of increasing electronegativity is Si<Se<C<O<F.